Power transistors which are mainly used in power supply circuits have conventionally been provided in various electric appliances such as those for use in households, and various packages and modules for such power transistors have been proposed according to purposes. Furthermore, recent environmental awareness has drawn attention to new uses of a power device and a power module each including a power transistor in an electric vehicle, a solar power generation device and a wind power generation device etc. Therefore, such a power device and a power module have been required to be more resistant to high voltages, generate a large current, and become small and lightweight.
Furthermore, in addition to the above requirements, the power device and the power module are also required to improve their switching speed. Therefore, it has been particularly necessary to reduce not only resistance and inductance attributed to wiring in a package but also resistance and inductance attributed to external connection terminals.
In general, packages of the above power device and the like are standardized packages (TO-220 or TO-3P etc.). Since there has conventionally been no need to take resistance and inductance into consideration, a wire bonding connection has been employed for connection between a semiconductor chip and a lead terminal serving as an external connection terminal in a package. For the wire bonding connection, a thin wire (gold or aluminum etc.) has been used.
However, a thin long wire has a large resistance and inductance. Therefore, it is difficult to reduce the resistance and inductance as required at present.
In view of the circumstances, there has been proposed a method of directly connecting the lead terminal and the semiconductor chip without using a thin wire. For example, Patent Literatures 1 and 2 each disclose a method including (i) forming specific bumps on electrodes of a semiconductor chip, (ii) mounting the semiconductor chip on a lead frame, and thereafter (iii) placing lead terminals which have been processed in a shape that can be joined to the bumps of the semiconductor chip to thereby connect the lead terminals to the bumps. According to the method, it is possible to electrically connect the lead terminals and the semiconductor chip with small resistance and inductance.